Senate Judiciary Chairman Patrick J. Leahy on Tuesday introduced a new surveillance overhaul bill that has the backing of civil liberties groups, but leaves an open question about what a House and Senate compromise on intelligence might look like.

Leahy’s bill would ban bulk government collection and storage of telephone metadata under Section 215 of the law known as the Patriot Act. If passed, the Vermont Democrat said the bill “would represent the most significant reform of government surveillance authorities since Congress passed the USA Patriot Act 13 years ago.”